The present invention is directed to a two-way messaging system, and more particularly to a system and method for expanding the capacity of a paging system for receiving high inbound-traffic from stationary pager sites.
Prior art two-way pager networks support multiple subscriber units (SUs) with both outbound messages to the SUs and inbound messages from the SUs to a network base station. In a standard ReFLEX.sub..TM. -based system, a two-way pager protocol promulgated by Motorola, Inc. of Schaumberg, Ill., the inbound traffic consists primarily of acknowledgments and short menu-based routine messages. Standard ReFLEX.sub..TM. systems primarily support low power mobile subscriber units with heavy outbound traffic and only light inbound traffic.
There exists a need to support a two-way pager network having a large number of mostly stationary SUs, whose message requirements are directed to heavier inbound communications traffic. An application of this sort may include a fixed-site SU for sending frequent status reports paging messages, such as with a vending machine, credit card verification system, meter reading, etc. One example of this application is connecting an SU to a vending machine to transmit, upon request, the status of various vending parameters (number of cookies remaining, coins accumulated, last service date, etc.).
FIG. 1 depicts a prior art two-way pager system infrastructure. FIG. 1 depicts elements of a two-way pager network 100 operating within a geographical region 102. A central base station 104 sends messages to individual two-way SUs 106 within region 102 via transmit/receive (TX/RX) sites 108. A simultaneous outbound transmission to more than one SU 106 is known as a simulcast, and the receiving SUs are within a region 102 known as a simulcast area. In response, individual SUs 106 send inbound messages to the central base station 104, received and forwarded by either the TX/RX sites 108 or a plurality of receive-only (RX-only) sites 110. Each of the TX/RX sites and RX-only sites are known as a base station for purposes of the present application. The central base station 104 includes a central receiver and switching center, to which all messages are forwarded. The additional RX sites 110 are required when the transmission coverage area of the TX/RX sites 108 exceeds the reception coverage area.
FIG. 2 depicts a block diagram of a prior art base station network 200 of the two-way pager network 100. As described above, central base station 104 receives inbound messages from multiple SUs (not shown) via TXIRX sites 108 and RX sites 110, which are base stations hereafter collectively referred to as "receivers." The central base station 104 further includes a message switching center ("switch") 114 and an RF network controller, herein referred to as a central base station controller 112.
The central base station controller 112 schedules inbound and outbound messages according to requirements obtained from the switch 114 and from the SUs 106. Inbound transmissions are divided among scheduled and unscheduled inbound transmission time slots. Each SU 106 is assigned a unique identifier address which, being transmitted along with each SU's 106 inbound transmission, associates an inbound message to a specific SU 106. In prior art two-way pager networks 100, including the standard ReFLEX.sub..TM. system, no more than one SU 106 is scheduled for transmission in any area 102 during any given scheduled transmission time slot. This is primarily caused by the radio equipment in prior art networks, composed of an omnidirectional antenna and a single receiver 108 or 110, not being able to decode more than a single message at a time. This is also due in part due to functional limitations of the central base station controller 112, which, in a given simulcast area 102, can receive only one inbound message per time slot.
A two-way pager network developed by Wireless Online, Inc., the assignee of the present application, employs a multibeam antenna having a receiving channel associated with each beam. This equipment allows for simultaneous reception of an SU message on each channel. However, without the benefits of the embodiments of the present invention herein described, the central base station of two-way pager networks will not be able to support multiple simultaneous inbound SU messages.
There is thus a need for a system and method for expanding the inbound message capacity of a two-way pager system 100 to support simultaneous transmissions from multiple SUs 106. The system must also support fixed-site SUs having status-report transmission requirements. Additionally, the system and method must support high inbound capacity without affecting the existing architecture of standard two-way pager networks 100, including ReFLEX.sub..TM. systems.